1. Field of the Invention
The present invention relates to an electronically controlled fuel injection apparatus for an internal combustion engine, and particularly to an apparatus for stabilizing the engine speed under idling condition.
2. Description of the Prior Art
In a conventional electronically controlled fuel injection apparatus, it is common to supply an amount of fuel injection which is proportional to the amount of suction air per excursion of the engine or the amount of suction air per excursion divided by an engine rotation speed. In an idling mode or constant velocity running mode, however, a constant and stable engine output is required. The engine output or the engine rotation speed, however, changes due to external disturbances such as small change in a load or variance in a burning rate, and unstable idling state or surging takes place. Such problems are serious particularly when a lean air-to-fuel ratio is set to reduce air pollusion by exhaust gas or exhaust gas recirculation control value (EGR) is used, or when a low idling rotation is set to save fuel consumption.
In a prior art system, the amount of fuel injection is changed when the amount of suction air or the engine rotation speed changes to compensate for the change in the load or the rotation speed. However, the compensation based on the amount of suction air or the engine rotation speed (at least one rotation) cannot completely compensate for the stability of the engine.